From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756234Ab1LWBzh (ORCPT ); Thu, 22 Dec 2011 20:55:37 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:47287 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754004Ab1LWBzd (ORCPT ); Thu, 22 Dec 2011 20:55:33 -0500 Date: Thu, 22 Dec 2011 17:58:34 -0800 From: Andrew Morton To: Vivek Goyal Cc: Tejun Heo , avi@redhat.com, nate@cpanel.net, cl@linux-foundation.org, oleg@redhat.com, axboe@kernel.dk, linux-kernel@vger.kernel.org Subject: Re: [PATCHSET] block, mempool, percpu: implement percpu mempool and fix blkcg percpu alloc deadlock Message-Id: <20111222175834.66559c8b.akpm@linux-foundation.org> In-Reply-To: <20111223014043.GC12738@redhat.com> References: <1324590326-10135-1-git-send-email-tj@kernel.org> <20111222135925.de3221c8.akpm@linux-foundation.org> <20111222220911.GK17084@google.com> <20111222142058.41316ee0.akpm@linux-foundation.org> <20111223014043.GC12738@redhat.com> X-Mailer: Sylpheed 2.7.1 (GTK+ 2.18.9; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 22 Dec 2011 20:40:43 -0500 Vivek Goyal wrote: > That's why the need of per cpu data structures to make stat collection > lockless. btw, (and this is a common refrain): was there any reason for avoiding using percpu_counters here? afacit these stats don't have the transient-negative-number problem because they're purely upcounters, but percpu_counters would be helpful when num_online_cpus is much less than num_possible_cpus. Plus it would avoid implementing yet another hand-coded percpu_counter...